OBJECTIVES: 1. The role of alloantigens in the natural killing will be further investigated by cold target competition experiments. 2. The human lymphocyte subsets which do not exert natural killing and are not induced for it by IFN (the high avidity E rosetting cells) will be triggered for cytotoxicity by lectins. The characteristics on this system will be compared with the natural, and IFN induced system, with special emphasis on target selectivity. 3. The two human lymphocyte subsets - one acting on K562, the other on K562 and Daudi will be characterized with the monoclonal reagents for suppressor and helper T cells and monocytes. 4. The H-2 restriction of cytotoxic lymphocytes in the methylcholanthrene sarcome system will be studied in vitro. Special emphasis will be placed on the contribution of the f1 anti parental effect. 5. The effect of viral vaccination on the natural killer potential of human blood lymphocytes will be evaluated in parallel with the activation of cells as measured by DNA synthesis. 6. The events in the mixed autologous cultures - T and B cells - will be analyzed. The generation of cytotoxic cells with specificity and the unselective lytic effects will be studied.